1. Field of the Invention
The present invention relates to a double-lobe type rotor design process which is able to create a defined rotor and a conjugate rotor intermeshing and conjugating to each other from carryover to suction and from exhaust to the end of the completed operation period by different parameters, and evaluate optimal rotor profiles to be used for some systems like a vacuum pump, an air booster, a compressor and a supercharger, enhancing compression ratio, providing a smooth suction and exhaust process and avoiding noise and vibration.
A double-lobe type rotor used in multistage type vacuum pumps, compressors, air boosters or superchargers generally comprise a defined rotor and a conjugate rotor intermeshing to each other. A pair of lobes of each rotor provides periodic compression operation of gas suction and gas exhaust. Therefore, the meshing mechanism of two lobes of the rotors is very important. If the meshing mechanism of the two lobes of the rotors is not good enough, noise and vibration may occur during the periodic gas suction, gas exhaust, and carry over processes of the rotors. Moreover, wear may occur due to the improper intermeshing of the rotors thereby reducing the durability of operation.
U.S. Pat. Nos. 1,426,820, 4,138,848, 4,224,016, 4,324,538, 4,406,601, 4,430,050 and 5,149,256 disclose relevant rotors. Referring to FIG. 9, lobes of a pair of rotors 8, 9 of U.S. Pat. No. 5,149,256 include a tip portions 82, 92 formed at ajunctions between the concave portions 80, 90 and the arcuate surfaces 81, 91 so that there is discontinuity of the rotors 80, 90 's curves. Therefore, during the moments from inefficient compression period to the period of air's starting intake, the top portions 83, 93 of the rotors 8, 9 will operate unsmoothly at the tip portion 82, 92 thereby resulting in noise and vibration.
To overcome the defects mentioned above, U.S. Pat. No. 6,776,594 provides two rotors with smooth operation curve and conjugate to each other. The main feature is that the operation curve provided by the rotors from the carryover period to the period of starting suction and from the exhaust period to the end is defined by a couple of smoothly connected curves rather than a couple of connected arc and concave curve, thereby avoiding noise and vibration during the periodic operation of suction, exhaust, and carryover, etc